Ignition coil for internal combustion engine

Abstract

In a stick coil, there is disclosed an ignition coil for an internal combustion engine which can prevent a crack (a collar leak) from being generated due to a thermal stress. In this ignition coil, the structure is made such that a size (L) of a portion which is in parallel to an axial direction of a primary spool ( 121 ) in a projection portion ( 121 b ) is larger than a size (T) of a portion which is in parallel to an orthogonal direction to the axial direction of the primary spool ( 121 ). Accordingly, a frontal projected area of the projection portion ( 121 b ) as seen from a flowing direction of a resin becomes small, a resin flow is hard to get out of order at a time when the resin flows through a portion corresponding to the projection portion ( 121 b ) at the forming time, and a convoluted void and a weld are hard to be generated. Accordingly, since it is possible to prevent a mechanical strength in a root portion of the projection portion ( 121 b ) from being reduced, it is possible to previously prevent a crack from being generated in the root portion of the projection portion (the collar portion) ( 121 b ) due to a thermal stress so as to reduce an insulating property.

1. An ignition coil for an internal combustion engine comprising:
 an integrally formed resin spool and a coil constituted by a coil winding wound around said spool; and  
 a high electric voltage being supplied to an ignition apparatus in the internal combustion engine,  
 wherein said spool is provided with a cylinder portion around which said coil is wound, a collar portion protruding to an outer side in a diametrical direction from an end side outer peripheral surface of said outer portion so as to form a circumferential shape, and a reinforcing portion connected to said collar portion, extending in an axial direction of said cylinder portion and reinforcing said collar portion, and  
 wherein a ratio of thickness (t/t0) of a thickness (t) of said collar portion and/or the reinforcing portion with respect to a thickness (t0) of said cylinder portion is equal to or less than 1.5.  
 
   
   
     2. The ignition coil for an internal combustion engine as claimed in  claim 1 , wherein said ratio of thickness (t/t0) is equal to or less than 0.1. 
   
   
     3. The ignition coil for an internal combustion engine as claimed in  claim 1 , wherein said reinforcing portion is extended from a substantially center of said collar portion and form a substantially T shape with said collar portion. 
   
   
     4. The ignition coil for an internal combustion engine as claimed in  claim 1 , wherein said reinforcing portion is extended from both end sides of said collar portion and form a substantially U shape with said collar portion.